Showing papers on "Magnetic circuit published in 2000"

Design and finite-element analysis of an outer-rotor permanent-magnet generator for directly coupled wind turbines

Abstract: This paper presents the design and finite-element analysis of a permanent-magnet generator using neodymium-iron-boron magnets for directly coupled wind turbines. For the sake of small size and light weight with extra low speed for direct coupling, the outer rotor structure is used. The simple magnetic equivalent circuit approach is used for initial design iteration, and the finite-element method is applied to analyze the detailed characteristics. Comprehensive experimental tests were conducted to verify the theoretical predictions. Agreement between the theoretical work and testing results was good.

Magnetic circuit model for the mutually coupled switched-reluctance machine

Abstract: The mutually coupled switched-reluctance motor (SRM) appears to have several performance advantages over other motor technologies. The existence of strong coupling between phases, however, makes the analysis of this machine quite complicated. Preliminary design of this machine can be greatly accelerated by the ability to evaluate potential motor geometries quickly. This paper introduces a general magnetic circuit model of the mutually coupled SRM that adapts to any geometry, unlike existing geometry-dependent approaches (such as finite elements), which are numerically intensive and require excessive computation time. The model uniquely implements the magneto-motive force (mmf) sources necessary to accommodate complex flux paths through the machine and includes the effects of magnetic saturation. The results are compared to those of a finite element solver to demonstrate the performance of this method as a first-step to evaluating candidate designs.

Nonlinear varying-network magnetic circuit analysis for doubly salient permanent-magnet motors

Abstract: In this paper, a nonlinear varying-network magnetic circuit (VNMC) modeling method is developed for doubly salient permanent-magnet (DSPM) motors. The method is used to analyze the static characteristics of DSPM motors by specific performance calculations, in which the interaction between the permanent-magnet field and the armature current field, as well as magnetic saturation, are taken into account. Two newly proposed DSPM motors (12/8-pole and 6/4-pole) are used as examples. There is good agreement between the results of the nonlinear VMMC modeling method and finite-element analysis. Moreover, the nonlinear VNMC method offers the advantage of calculating, effectively and efficiently, the static characteristics of DSPM motors having different dimensions, parameters, and conditions. Finally, the proposed method is verified by experimental testing of a 6/4-pole prototype.

Magnetic field measurements with a novel surface micromachined magnetic-field sensor

Abstract: The surface micromachining process of Robert Bosch GmbH has been used to fabricate a novel type of magnetic-field sensor. The Lorentz force, caused by the interaction of a current and an external magnetic field in a suspended surface micromachined conducting beam, laterally displaces the suspended structure. The displacement of the structure is converted into a capacitance change by comb-electrodes, which form a differential capacitor. An appropriate electronic circuitry measures the magnetic field by quantifying the displacement of the conducting beam. In order to increase sensitivity to magnetic fields, the magnitude of the deflection is increased by resonant operation in a vacuum ambient. The sensor obtains its vacuum environment by encapsulation with a new wafer bonding process. Prototype sensors with resonant frequencies in the range around 1300 Hz show Q-factors above 30. With these samples, relative magnetic sensitivities of 900 000 (V/A/spl middot/T) with a detection limit in the sub /spl mu/T-range are reported.

Switching DC-to-DC converter utilizing a soft switching technique

Abstract: Soft switching DC-to-DC converter achieves simultaneously ultra high efficiency and very small size owing to a new magnetic circuit structure and a corresponding novel converter circuit configuration with special properties. Unique magnetic design also provides an overload current capability of several times the nominal load current. Despite its simple implementation requiring only proper drive timing of the switching devices, the unique soft-switching methods result in nearly complete elimination of switching losses over the entire operating range. This, in turn, permits operation at even higher switching frequencies, and leads to further reduction in size and weight.

Low inductance electrical machine

Abstract: A low inductance electrical machine (1) that may be used as an alternator or motor with low armature inductance is disclosed. Arrangements of complementary armature windings (40A, 42A) are presented in which the fluxes induced by currents in the armature windings (40) effectively cancel leading to low magnetic energy storage within the machine (1). This leads to low net flux levels, low core losses, low inductance and reduced tendency toward magnetic saturation. The inclusion of additional gaps (54, 56) in the magnetic circuit allows for independent adjustment of air gap geometry and armature inductance. Separately excited field arrangements (8) are disclosed that allow rotor (22, 24, 25) motion to effect brush-less alternator or brush-less motor operation. An exemplary geometry includes a stator (2) including two annular rings (4, 6) and a concentric field coil (8) together with a rotor structure (22, 24, 25) separated from the stator (2) by four air gaps (50, 52, 54, 56).

Magnetic workholding device

Abstract: A magnetic device includes a cylindrical outer pole having a central axis and formed of a ferromagnetic material including a circular base and a cylindrical sleeve defining an outwardly opening cylindrical cavity. A reversible magnetic unit located in said cavity includes a cylindrical core having a magnetic axis aligned with the central axis and a normal magnetic polarity in an inactive state. A cylindrical inner pole formed of a ferromagnetic material is operatively coupled to the core and inwardly radially spaced from said sleeve. An annular band between said sleeve and said inner pole formed of a permanent magnetic material has a magnetic polarity transverse to said central axis and magnetically aligned with said normal magnetic polarity of the core whereby an internal magnetic circuit is established in the inactive state through the poles, the core and the permanent magnet to the exclusion of said workpiece. When the polarity of the core is reversed an external circuit is established between the poles for magnetic coupling with the workpiece.

Method and device for controlling the magnetic flux in a rotating high voltage electric alternating current machine

Abstract: A rotating electric machine for direct connection to high-voltage networks, in which the magnetic circuit adapted for high voltage comprises a rotor, stator and main and auxiliary windings in operative relation. At least one of the windings is a conductor surrounded by a magnetically permeable, field confining insulation system.

Optimization of a magnetically saturable interior permanent-magnet synchronous machine drive

Abstract: Interior permanent magnet (IPM) synchronous machines are attractive because they can achieve constant-power operation over a wide speed range with limited magnet strength requirements and reduced power electronics cost These characteristics provide the IPM machine with advantages over alternative machine types in applications such as spindle and traction drives An important challenge for high-performance IPM machine design is to model the magnetic saturation of the core in a manner that is accurate, flexible, and computationally fast for design optimization A magnetically-saturable lumped parameter model (LPM) is developed for the optimized design of high-performance IPM synchronous machine drives Using equivalent magnetic circuit analyses, the dq-frame inductances and magnet flux linkage are calculated for transversely-laminated IPM machines The lumped parameters are employed to predict machine drive system performance for both rated-torque and constant-power operation The results of saturable model calculations and finite element analysis (FEA) match very closely for the machine inductances, magnet flux linkage, and converted torque Further validation is presented by comparing measurements of existing experimental machines to predictions from the saturable lumped parameter model Agreement of measurements and predictions for the highly nonlinear saturable q-axis inductance is within 5% in the saturated excitation range The utility of the saturable LPM is then demonstrated by developing a cost-optimized design for an automotive integrated starter/generator (ISG) that is rated at 4 to 6 kW during generating operation This ISG machine is mounted in a direct-drive mechanical configuration on the engine crankshaft Agreement between the saturable LPM and FEA calculations for q- and d- axis inductances and PM flux linkage are all within 5% for the entire excitation range Results of this model have been combined with structural FEA and demagnetization studies to produce a machine design that is predicted to meet all key ISG performance requirements For this application and the chosen cost model, it is shown that optimizing the combined machine and drive system versus optimizing only the machine reduces the overall cost prediction by 12%

Magnetic bearing system

Abstract: The invention relates to a magnetic bearing for generating magnetic forces. A configuration of electromagnetic poles and of permanent magnetic poles which, to the greatest possible extent, is planar enables the generation of a magnetic flux in the air gaps toward the rotor, also in the de-energized state. If this flux is modulated using a control flux, magnetic forces can be exerted upon the rotor for the purpose of providing magnetic support. This configuration makes it possible to provide magnetic bearings of a simple mechanical design.

Chapter 2 – Modeling of Giant Magnetostrictive Materials

Abstract: Publisher Summary The chapter describes the models that are used to understand the modeling of giant magnetostrictive materials. Stress and strain are adopted to understand the magnetoelastic processes. A characteristic property of magnetostrictive materials is that a mechanical strain occurs if they are subjected to a magnetic field in addition to the strains originated from pure applied stresses. Their magnetization changes due to changes in applied mechanical stresses and applied magnetic field. Magnetizing coil and magnetic circuit are assumed to function ideally. The magnetostrictive rod needs to have a physical coil with a certain resistance, and the magnetic circuit will show a flux leakage and a certain amount of reluctance. The rod end has to be connected to a mechanical transmission link with some compliance that transfers the mechanical power to the mechanical load. All these things affect the magnetomechanical performance along with the parameters of a physical actuator comprising magnetostrictive materials.

Magnetic rotational position sensor having dual magnetic flux sensor capabilities

Abstract: A magnetic rotational position sensor for sensing each rotational position of a control shaft about a first axis over a definable range of rotation. The position sensor generally includes a magnetic circuit and a pair of magnetic flux sensors. The magnetic circuit is comprised of a ring pole piece defining an air gap area and a magnet disposed within the air gap area. The ring pole piece and the magnet cooperate to produce a magnetic field within the air gap area. The magnetic circuit is adjoined to the control shaft to synchronously rotate the magnetic field about a second axis. The pair of magnetic flux sensors are disposed within the magnetic field to sense each rotational position of the control shaft as the control shaft is rotated about the first axis over the definable range of rotation.

An electric multipole motor/generator with axial magnetic flux

Abstract: This invention relates to an electric multiple motor/generator with axial magnetic flux. Thus a generator/motor or electrical machine in which a magnetic flux path through one or more pole legs or pole cores surrounded by current windings or coils is provided. This allows a high density of the magnetic flux to be passed through the pole legs or cores, which results in a low consumption of material for the pole legs or pole cores compared with prior art machines, where for example a large stator diameter may be needed in order to conduct a high magnetic flux. Additionally the generator/motor or electrical machine is very efficient both at a low and a high number of revolutions. According to another aspect of the invention a multiple phase output without enlarging the diameter of the generator is provided.

Optimized Realization of Fault-Tolerant Heteropolar Magnetic Bearings

Abstract: Flux coupling in heteropolar magnetic bearings permits remaining active coils to assume actions of failed coils to produce force resultants identical to the un-failed actuator. This fault-tolerant control usually reduces load capacity because the redistribution of the magnetic flux which compensates for the failed coils leads to premature saturation in the stator or journal. A distribution matrix of voltages which consists of a redefined biasing voltage vector and two control voltage vectors can be optimized in a manner that reduces the peak flux density. An elegant optimization method using the Lagrange multiplier is presented in this paper. The linearized control forces can be realized up to certain combination of 5 poles failed for the 8 pole magnetic bearing. Position stiffness and voltage stiffness are calculated for the fault-tolerant magnetic bearings, Simulations show that fault-tolerant control of the multiple poles failed magnetic bearings with a horizontal flexible rotor can be achieved with reduced load capacity.

Analysis of orthogonal-core type linear variable inductor and application to VAr compensator

Abstract: This paper presents a quantitative analysis of the orthogonal-core type linear variable inductor. The orthogonal-core has wedge gaps for reduction of harmonics of the output currents. The analysis is based on a 3-dimensional nonlinear magnetic circuit of the orthogonal-core. Using the magnetic circuit, one can calculate accurately the operating characteristics of the variable inductor. Furthermore, they develop a VAr compensator for a 6.6 kV AC distribution system using the three-phase variable inductor.

Vibration actuator having an elastic member between a suspension plate and a magnetic circuit device

Abstract: A vibration actuator in which a magnetic circuit device (1,2,3) is elastically suspended to a vibration transmitter (12) by a suspension plate (5) in a predetermined direction, a primary elastic member (6a) is interposed between the suspension plate and the magnetic circuit device in the predetermined direction. A coil (10) is fixed to a vibrating member (9) and disposed in a magnetic gap of the magnetic circuit. It is preferable that the suspension plate has a leaf spring portion extending along a spiral curve between central and peripheral portions thereof.

Operating apparatus for switching device

Abstract: In a closing magnetic circuit, when a movable contact is in contact with a fixed contact and a switching device is closed, N and S poles of a permanent magnet attract the fixed member in a direction in which the movable contact is pressed against the fixed contact. In an opening magnetic circuit, when the movable contact is separated from the fixed contact and the switching device is open, one of the N and S poles of the permanent magnet attracts the fixed member in a direction in which the movable contact is separated from the fixed contact. An operating electromagnet winding increases and decreases the magnetism in the closing magnetic circuit and opening magnetic circuit. With this configuration, it is possible to realize an operating apparatus for a switching device using a simple mechanism and assure a stable operation by producing a great contact load.

Thermally protected electric machine

Abstract: An electric machine including a magnetic component, forming part of its rotor or stator that loses its magnetic characteristics above a certain chosen temperature is disclosed. This magnetic material forms part of a magnetic circuit that guides flux about the stator. As a result, any magnetic flux emanating with the rotor stops circulating about the stator above this temperature, and the machine stops acting as generator. The component is thermally coupled to windings carrying current from the machine's stator. The material forming the component is selected so that the chosen temperature is lower than the temperature at which the machine would be thermally damaged. This, in turn, limits the operating temperature of the windings, and thus prevents overheating of the machine during operation, typically caused by a fault. Preferably this magnetic material is formed from a ferrite material, such as a Manganese Zinc ferrite material.

Electric-acoustic transducer having dual voice coil drivers

Abstract: In the electric-acoustic transducer, first to third permanent magnets are respectively received in the first to the third recesses of a yoke, so as to generate non-alternating magnetic fields. The first and second magnetic gaps are formed between the yoke and the first and the second plates. The first and the second coils are respectively disposed in the first and the second magnetic gaps, to generate alternating magnetic fields of the same phase, when an electric driving signal is applied from the exterior. The electric-acoustic transducer achieves reproduction of a broad frequency band with high power and high efficiency, even with an ultra slim or small dimension, proper for a small electronic appliance such as a notebook computer, by employing dual voice coil drivers and auxiliary magnetic circuits.

Electromagnetic apparatus employing high permeability low conductivity element

Abstract: A pole for use in a magnetic circuit includes a flux-passing portion for passing magnetic flux and a cap. The flux-passing portion has a face through which at least some of the magnetic flux passes and to which the cap is fixed. The cap is made of a permeable material and is formed to impede eddy currents in the cap. The cap may have a top and bottom surface joined by a shoulder to provide a distribution of magnetic flux through the shoulder that is less concentrated than the flux distribution through a 90-degree corner. The pole may be incorporated into a generator, a motor, a linear motor, or a portable engine-driven generator to increase the efficiency thereof.

A sensorless method to determine the static armature position in an electronically controlled solenoid device

Abstract: A method is provided to determine a static position of an armature 24 of an electronically controlled solenoid device 10. The method provides an electronically controlled solenoid device having a first stator 14 and a first coil 16 operatively associated with the first stator, a second stator 18 and a second coil 22 operatively associated with the second stator, and an armature 24 mounted for movement between the first and second stators. The armature defines a magnetic circuit with each of the first and second stators and their associated coils. A rate of change of flux of a magnetic circuit associated with each coil is ramped in a generally linear manner over a period of time. A nominal position of the armature is defined where current in both of the coils is substantially equal. A current slope of each of the coils resulting from the associated ramped rate of change of flux is observed. An offset of each current slope from the nominal position is indicative of the static position of the armature.

Vibration actuator having three vibration modes

Abstract: In a vibration actuator using a magnetic circuit device (14), a supporting arrangement (23) elastically supports the magnetic circuit device. A coil (17) is inserted into a magnetic gap (15) of the magnetic circuit device and is supported by a vibration plate (19). The vibration actuator has a first operation mode in which the magnetic circuit device mainly vibrates to transmit vibration through the vibration plate to the outside, a second vibration mode in which the coil mainly vibrates to produce a buzzer sound through the vibration plate, and a third vibration mode in which the magnetic circuit device and the coil mainly vibrate to produce a sound corresponding to a speech through the vibration plate.

Stage device and exposure system

Abstract: PROBLEM TO BE SOLVED: To provide a stage device or the like which is capable of positioning a stage with high accuracy, where a magnetic field is less disturbed. SOLUTION: In figure, coil joints 16 each T-shaped in cross section on an XZ plane and extending in a Y direction are provided on an upper and a lower part of the left side of a slider plate 15 respectively as they are protruding sideward. A movable coil (movable piece) 17 is provided to the tip of the coil joint 16. The movable piece 17 is inserted into the U shape of a U-shaped yoke 12 to form a linear motor which generates a driving force in a Y-direction. The intersection of the driving forces of the linear motors which are arranged apart from each other in a vertical direction is nearly coincident with the position of the center of gravity of the slider 4. Permanent magnets 9 and 10 are arranged on the inner wall surfaces of the U-shaped groove of the yoke 12, as they are confronting each other through a certain gap. The permanent magnets 9 and 10 shown in Figure are all so arranged as to set their S poles above their N poles. The magnetic flux of the four permanent magnets 9 and 10 forms a closed magnetic circuit and hardly leaks out. COPYRIGHT: (C)2003,JPO

Fault tolerance of magnetic bearings with material path reluctances and fringing factors

Abstract: An equivalent magnetic circuit of an eight-pole heteropolar magnetic bearing with path reluctances is developed with nondimensional forms of flux, flux density, and magnetic force equations. The results show that fluxes and magnetic forces are considerably reduced for the magnetic circuit with relatively large path reluctances. A Lagrange multiplier optimization method is used to determine current distribution matrices for the magnetic bearing with large path reluctances. A cost function is defined in a manner that represents load capacity in a specific direction. Optimizing this cost function yields distribution matrices calculated for certain combinations of five poles failed out of eight poles. Position stiffnesses and voltage stiffnesses are calculated for the fault-tolerant magnetic bearings. Fault-tolerant control of a horizontal rigid rotor supported on multiple-coil failed magnetic bearings including large path reluctances is simulated to investigate the effect of path reluctances on imbalance response.

A simplified method for the iron losses prediction in soft magnetic materials with arbitrary voltage supply

Abstract: The aim of this work is to propose a new approach for the iron losses prediction, in soft magnetic materials with any voltage supply, starting from the knowledge of the iron losses with sinusoidal supply. The model is based on the separation of the loss contributions due to hysteresis, eddy currents and excess losses with sinusoidal supply. Since any contribution depends on the voltage supply characteristics, it is possible to find a direct mathematical relationship between the iron loss contribution and the voltage supply characteristics. As a consequence, an iron loss prediction can be obtained with any voltage supply, which does not produce hysteresis minor loop. The energetic model is based on coefficients that depend on the material characteristic. An accurate analysis of the model on eight magnetic materials, of different thickness and alloy, has been made, so the main coefficients for a large spread of magnetic materials, used for the electrical machines construction, have been found. The paper can be a useful support for electrical machine designers when the energetic performances of magnetic material, have to be predicted with the voltage supply different from the sinusoidal one.

Compact THz-radiation source consisting of a bulk semiconductor, a mode-locked fiber laser, and a 2 T permanent magnet

Abstract: A compact THz-radiation source using an InAs semiconductor is demonstrated with a turn-key femtosecond fiber laser as an excitation source and a newly designed 2 T permanent magnet. By using a newly designed magnetic circuit, a compact permanent magnet which can exceed the remanence magnetic field was obtained. This compact source is sufficiently intense for absorption spectroscopy.

Vibrator with vibration transmitter and its fitting structure

Abstract: PROBLEM TO BE SOLVED: To perform stable and strong vibration for calling by transmitting the vibration of a vibrator, which is the call-incoming reporting means of a portable terminal set, directly to a carrying person of the portable terminal set. SOLUTION: The vibrator provided with a diaphragm, a magnetic circuit part arranged opposing the diaphragm, a spring for supporting the magnetic circuit part, a housing for supporting the diaphragm and the magnetic circuit part, and a voice coil, is provided with the vibration transmitter on bottom face of the yoke of the magnetic circuit to transmit the vibration of the vibrator directly to the carrying person. COPYRIGHT: (C)2002,JPO

Analysis of a magnetic bearing pair with a permanent magnet excitation

Abstract: An analysis of the magnetic circuit of magnetic bearings with a permanent magnet excitation is reported. Applicability of analytical, coupled 2D FEM and 3D FEM models for the magnetic field is discussed. The comparison between different methods is given.

Oil check sensor

Abstract: PROBLEM TO BE SOLVED: To provide an oil check sensor capable of quantitatively detecting the amount of metal powder in engine oil and eliminating the need for the removal and cleaning of a sensor part at the time of measurement. SOLUTION: This oil check sensor is provided with a sensor head 40 with a pair of coil heads 45a and 45b to be immersed in oil, an exciting circuit 20 for magnetizing a detecting head, and a yoke 30 to connect the exciting circuit 20 to the censor head 40. The oil check sensor is further provided with a magnetic detecting circuit 50 for detecting changes in magnetic flux density which occur in a magnetic circuit constituted of the exciting circuit 20, the yoke 30, and the gap between the coil heads 45a and 45b according to the adhesion of metal powder to the coil heads 45a and 45b.